1. Field of the Invention
This invention relates to an outer appearance inspection of a printed circuit pattern, and more particularly a pattern inspection method and an apparatus therefor which is suitable for allowing a specified amount of unevenesses in case that a pattern has certain expected unevenesses in its contour and for making a positive inspection of only a detrimental defect.
2. Description of the Related Art
As an example, a circuit pattern drawn in a ceramic green sheet has, as shown in FIG. 2, several unevenesses (a) at its pattern edges. Since the unevenesses (a) of the pattern edges are not a circuit pattern defect, it is necessary not to make an erroneous identification of the unevenesses (a) as defects like unevennesses (b) to (e) which are original detrimental defects (open (circuit) b, semi-open (circuit) c, short (circuit) d, and semi-short (circuit) e) are to be inspected.
In case that the above-described circuit pattern is to be inspected, as described in the conventional system of U.S. Pat. No. 4,654,583, the inspected pattern is binarized and this binarized pattern is expanded and contracted by a specified amount. Thereafter a connectivity of patterns between the specified positions is compared with a good product data or a design data so as to inspect for defects.
In the case of the above-described patent, a presence or a non-presence of the defect can be inspected more accurately even in case that the pattern edges have some unevenesses. However, since the presence or non-presence of the defect is inspected as a unit of one connected pattern, it is not possible to specify a location of the defect in the pattern and this specifying operation is not considered.
However, the circuit pattern sheet made in recent years is made large in size and it shows a trend to cause a length of one pattern to be elongated. Thus, even if the presence of absence of a defect can be detected, the prior art shows a problem that it takes much time to make a visual confirmation of the defect location of the pattern judged as having a defect, unless the specifying of the position of the defect in the circuit pattern can be performed. Much is consumed until the defect in the pattern is corrected.
In the known system, it is necessary to perform an extraction of connectivity of pattern in synchronism with an inspection of pattern in real time when a high speed inspection is to be performed. In general, since this process is troublesome, as disclosed in Jap. Patent Laid-Open No. 61-80376, the processing unit is complicated. Thus, the inspection device for realizing the high speed operation of the above-described system has a problem that it requires a high speed electric circuit having a large size and it is expensive in cost.